Wearable ultrafiltration device

ABSTRACT

An ultrafiltration device adapted to be worn on a portion of the body of a patient includes a blood inlet tube leading from a first blood vessel, a blood pump, an anticoagulant reservoir for infusing anticoagulants into the blood, a blood filter including a substrate through which the blood is circulated and filtered, a fluid bag for storing the excess fluid and a blood outlet tube leading to a second blood vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/846,618, filed May 14, 2004, entitled WEARABLE ULTRAFILTRATIONDEVICE, which is a continuation-in-part of U.S. Pat. No. 6,960,179,issued Nov. 1, 2005, entitled WEARABLE CONTINUOUS RENAL REPLACEMENTTHERAPY DEVICE, which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention is directed to ultrafiltration devices, and moreparticularly to a portable ultrafiltration device that may becontinuously worn by a patient.

BACKGROUND

Fluid overload can be caused by many things including metabolic disease,renal failure and, especially, congestive heart failure (CHF), which hasbecome a disease of epidemic proportions all over the globe. CHF is aprogressive deterioration of the heart muscle that leads to an inabilityto pump enough blood to support the vital organs. Deterioration of theheart muscle leads to decreased pumping capacity and increased fluidretention caused by the lack of perfusion pressure of the kidneys due tothe failure of the heart to pump enough blood at the proper pressure.Fluid overload can cause leg swelling, shortness of breath and wateraccumulation in the lungs, impairing the ability to properly breathe.

The incidence of class III and IV congestive heart failure (CHF)continues to grow along with the growing incidence of diabetes, obesity,coronary heart disease, Diastolic Dysfunction and other relatedailments. In addition, the medically improved outcomes from IschemicHeart Disease and Myocardial Infarction are generating an increasedpopulation of people suffering from varying degrees of CHF.

Treating patients with CHF is presently one of the major expenses in thehealthcare bill of any westernized nation. Furthermore, treatingpatients with CHF is one of the most significant causes of financialloss in the U.S. hospital industry.

Removal of excess fluids from the body can be accomplished withdiuretics and other drugs that improve the performance of the heartmuscle.

Thanks to numerous pharmacological agents such as ACE inhibitors,diuretics and beta blockers, the morbidity and mortality of CHF hasbecome somewhat improved. Pacemakers and implantable defibrillators haveaided in this regarding also.

Regardless of the advancements in medical technology some of the majorpatient problems associated with CHF are fluid overload and sodiumretention. Both fluid overload and sodium retention are associated withvarious endocrine derangements and release noxious cytokines that mayfurther aggravate the CHF condition. These drugs become graduallyineffective over time and may also cause undesirable effects such askidney failure.

There is a growing body of literature supporting the conclusion that thephysical removal of fluid by convection (i.e., ultrafiltration) of bloodcan significantly improve patient outcomes and shorten hospital staysand intensive care unit utilization. Fluid removal may be superior tothe administration of very large losses of diuretic drugs.

Advantages of ultrafiltration over diuretic drugs include: (1) efficientfluid removal without side effects such as kidney failure and bloodpressure drops; (2) prompt relief from shortness of breath and swelling;and (3) improvement regarding certain adverse hormonal effects that areassociated with CHF.

Ultrafiltration is performed by pumping blood from a catheter in anartery or a large vein, though a blood filter or a dialyzer whilecreating a gradient of pressure through the filter membrane. Thepressure gradient forces the passage of fluid out of the blood byconvection and the fluid is drained out.

Conventional ultrafiltration devices suffer from several drawbacks.Usually, these devices are cumbersome, heavy and must be hooked toelectrical outlets for power. Since ultrafiltration patients must remainconnected to these devices for many hours, their ability to performnormal every day activities is severely limited. In addition, typicalultrafiltration treatments are geared for fast removal of several litersof excess fluid. However, the fluid removal is only temporary and theexcess fluid usually reaccumulates in the patient's body after a shortperiod of time. The reaccumulation of fluid is harmful to the patients,as the kidneys are further injured by the progress of CHF and the sideeffects of the diuretic drugs used to treat the heart.

Presently ultrafiltration devices are not designed to economicallyprovide a single patient prolonged or continuous ultrafiltration. Inaddition, acute treatments performed over 4 to 6 hours of hemofiltrationon a patient, can be efficient and capable of removing up to around 23liters of excess fluid from a patient in one session, but are notphysiologically good for the patient and can be conducive of bluntshifts in fluid content in various compartments of a patient's body.Such large amounts of fluid removal may also create hypotension andhemodynamic instability. Furthermore, the present ultrafiltrationmethods do not provide for a steady removal of excess fluids and sodiumfrom the patient's body.

A further problem with ultrafiltration devices is that repeatedreconnection to an ultrafiltration device requires accessing blood flowby puncturing a large blood vessel and forming an arteriovenous shunt.These shunts only last for limited periods of time and are subject toinfection, clotting and other complications that result in numeroushospitalizations and repeated surgical interventions. Similar problemsalso exist when a patient's blood stream is accessed by alternativemethods, such as by inserting large catheters into large veins andarteries.

In view of the above disadvantages, there is a substantial need for aportable ultrafiltration device that provides continual, steady andsmooth removal of excess fluid from the body.

SUMMARY

Embodiments of the present invention alleviate to a great extent theabove-noted and other disadvantages by providing a portable, completelywearable ultrafiltration device that performs continuous, steady andsmooth removal of excess fluid from the body. Importantly, an exemplaryultrafiltration device does not require a patient to be hooked up to alarge machine for many hours a day, several days per week. Instead, anexemplary ultrafiltration device can conveniently be worn on a patient'sbody for continual use, 24 hours a day, seven days a week, providingsteady and smooth removal of excess fluid from the body and preventingthe shortness of breath and swelling that are associated with CHF.

One aspect of embodiments of the present invention involves anultrafiltration device adapted to be completely worn on a portion of thebody of a patient, including a blood pump and a blood filter forseparating excess fluid from the blood.

A further aspect an exemplary ultrafiltration device is that the deviceis in the form of a belt adapted to be worn about the waist, shoulder,thigh or other body portion of a patient, wherein the belt includes apair of end portions which are secured together by a belt fasteningmeans.

Another aspect of an embodiment of the present invention involves anultrafiltration device adapted to be completely worn on a portion of thebody of a patient includes a blood inlet tube leading from a first bloodvessel, a blood pump, an anticoagulant reservoir from whichanticoagulants are infused into the blood, a blood filter including asubstrate through which the blood is circulated and filtered, a fluidbag for storing the excess fluid and a blood outlet tube leading to asecond blood vessel.

These and other features and advantages of embodiments of the presentinvention will be appreciated from review of the following detaileddescription of the invention, along with the accompanying figures inwhich like reference numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the method and apparatus of the presentinvention may be obtained by reference to the following DetailedDescription when taken in conjunction with the accompanying Drawingswherein:

FIG. 1 is a perspective view of an embodiment of an assembly inaccordance with the present invention;

FIG. 2 is a perspective view of an embodiment of an assembly inaccordance with the present invention;

FIG. 3 is a perspective view of an embodiment of an assembly inaccordance with the present invention;

FIG. 4 is a perspective view of an embodiment of an assembly inaccordance with the present invention;

FIG. 5 is a perspective view of an embodiment of an assembly inaccordance with the present invention; and

FIG. 6 is a diagram of a wearable ultrafiltration device in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION

Ultrafiltration is a process by which excess fluid in the form of wateris removed from the blood, wherein the excess fluid in the blood ismoved from one side of a filtering device to another. The filteringdevice contains many hollow fibers made out of a semipermeable membrane.While blood flows inside of the hollow fibers, water and fluid from theblood moves through the membrane wall and is drained off. The purifiedblood remains inside the hollow fibers and is returned to the body.

Referring to FIG. 1, an ultrafiltration device 10 is designed to extracta targeted volume of fluid from the blood of a patient at a preciselycontrolled rate. The ability to predictably remove excess fluid from theblood reduces the risk of removing too much fluid too quickly, which canresult in low blood pressure and vital organ damage.

The ultrafiltration device 10 comprises a belt 20 adapted to be wornabout a portion of the body of the patient. According to someembodiments, the ultrafiltration device 10 is adapted to be worn aboutthe waist of the patient. However, as would be understood to those ofordinary skill in the art, the device 10 may also be worn about otherportions of the patient's body, such as over a shoulder or around athigh. According to some embodiments, the weight of the belt 30 is lessthan two pounds.

As seen in FIG. 1, the belt 20 includes a pair of end portions 70, 75,which are secured together by a belt fastening means 80 such as a buckle80, snaps 80, buttons 80 or hook and loop fasteners 80. The belt 20further includes a blood filter 30 including a blood inlet tube 33leading from a first blood vessel and a blood outlet tube 37 leading toa second blood vessel in the patient. The belt 20 also includes a bloodpump 60, which forces the patient's blood through the filter 30. Thepump 60 may be a shuttle pump, piston pump, roller pump, centrifugepump, piezoelectric pump, or other convention pump. Convention powersources 65 such as batteries 65 can be use to power the blood pump 60.

The blood filter 30 separates excess fluid from the patient's blood. Theexcess fluid is drained in to an excess fluid bag 50, which is to beperiodically emptied via tap 90. The fluid bag 50 can be positioned inthe vicinity of a thigh, a leg, an ankle, an arm, or any other suitablebody portion of the patient.

The coagulation of the blood circulating through the device 10 isprevented by the constant infusion of anticoagulant, which is infusedfrom an anticoagulant reservoir 95 through a port 105 and into the bloodinlet tube 33. In some embodiments, anticoagulant is infused using abattery powered anticoagulant pump 115. The pump 115 maybe a shuttlepump, piston pump, roller pump, centrifuge pump, piezoelectric pump, orother convention pump. Typical anticoagulants are infused into the blood150 include, but are not limited to, heparin, prostacyclin, lowmolecular weight heparin, hirudin and sodium citrate. According to otherembodiments, blood clotting inside the device 10 can be prevented by theoral administration of anticoagulent drugs including, but not limitedto, coumadin.

Referring to FIG. 2, according to some embodiments, the blood filter 30is a conventional blood filter 30 comprising a plurality of hollowfibers 310 having fixed, i.e., non-moving ends 321 through which theblood 150 flows. Blood filter 30 includes a housing 303, blood inlet305, a blood outlet 307 and a fluid outlet 315. The exterior walls 350of the hollow fibers 310 are semiporous so that excess fluid 135 in theform of water 135 and impurities 135 can be removed from the blood 150.As illustrated, each of fibers 310 a first, interior surface 311 incontact with blood 150 and a second, exterior surface 313 where excessfluid 135 is received. Blood inlet 305, interior surfaces 311 of fibers310 and blood outlet 307 define a blood side 317 of filter 30. Housing303 and exterior surfaces 313 of fibers 310 and blood outlet 307 definea blood side 317 of filter 30. Housing 303 and exterior surfaces 313 offibers 310 define a fluid side of filter 30 where excess fluid 135 fromblood 150 is received. As illustrated, blood side 317 of filter 30 isseparated from fluid side 319 of the filter by fibers 310. In theillustrated embodiment, fluid side 319 of filter 30 is enclosed exceptfor fluid outlet 315 such that the only fluid on fluid side 319 is fluidseparated from blood 150 and the only flow through fluid side 319 isexcess fluid filtered from blood 150 that exits filter 30 through fluidoutlet 315. As indicated by arrows 320, 330, excess fluid 135 is drainedfrom the hollow fibers 310, which act as a sieve such that excess fluid135 passes through, but not blood 150. The excess fluid 135 is drainedout of the filter 30 through fluid outlet 315 in a direction indicatedby arrow 145.

The blood 150 moves through the hollow fibers 310 under pressure fromthe blood pump 60. This pressure causes the excess fluid 135 in theblood 150 to filter out through the fiber pores, into the other side ofthe hollow fibers 310, from where the excess fluid 135 is drained out tothe fluid bag 50. The magnitude of pressure within the fibers 310determines the amount of net excess fluid 135 movement removed throughexterior walls 350. Small particles within the blood 150 are alsoremoved during this process, but particles larger than the blood filterpore size will be left behind in the blood 150.

Referring to FIG. 3, according to other embodiments, the blood filter 30is an alternative conventional blood filter 30 comprising a plurality ofparallel sheets 390 of semiporous material, wherein air 140 iscirculated on one side of the parallel sheets 390 and the blood 150circulates in the opposite direction on the other side of the parallelsheets 390. As illustrated, each of sheets 390 has a first surface 391in contact with blood 150 and a second surface 393 where excess fluid135 is received. The blood filters 30 of these embodiments areconventional and well known in the art. Excess fluid 135 and smallparticles are removed from the blood 150 through parallel sheets 390 anddrained off into excess fluid bag 50.

Referring to FIG. 4, according to some embodiments, the blood filter 50has a flexible casing 400 adapted to conform to the body contour of thepatient. In addition, the body-side wall 410 of each casing 400 isconcave to further correspond to bodily curves of the user. The casing400 can be made of any suitable material having adequate flexibility forconformance to the portion of the body to which it is applied. Suitablematerials include, but are not limited to polyurethane and poly vinylchloride.

Referring to FIG. 5, in an alternative embodiment, the blood filter 30includes a plurality of miniaturized blood filters 100, 110, 120, 130that remove impurities from the blood 150 of the patient. The number offilters, 110, 120, 130 in the plurality of filters, 110, 120, 130 may bevaried to reflect different ultrafiltration prescriptions. The pluralityof blood filters 100, 110, 120, 130 are connected in series, whereby theblood pump 60 forces the patient's blood 150, in a first direction,through the filters 100, 110, 120, 130, as indicated by arrows 165.Excess fluid 135 is drained from the blood filters 100, 110, 120, 130and into the excess fluid bag 50 as indicated by arrows 145. As would beunderstood by those of ordinary skill in the art, the filters 100, 110,120, 130 can also be connected in parallel without departing from thescope of the invention.

Referring now to FIG. 6, another exemplary embodiment of the presentwearable ultrafiltration device 600 is depicted. The wearableultrafiltration device 600 is built into or is part of a patientwearable belt or strap 602. The belt 602 includes at least a pair of endportions 604, 608 that are secured together by a fastening means (notspecifically shown) 610, 612 that could be any number of fasteningdevices suitable to secure the ends of a belt or strap togetherincluding, but not limited to snaps, buttons, buckles, laces, hoods andloops, zippers, etc.

A microcontroller 614 is utilized to control and monitor various aspectsof the exemplary wearable ultrafiltration device. The microcontroller614 is preferably a very low power microcontroller, but may besubstantially any microcontroller adapted to operate in theultrafiltration device. The microcontroller monitors the battery 616 orother acceptable power sources. The battery 616 is removably installedin the ultrafiltration device. The battery may also be recharged whileremaining in the device via a battery charger device connected to thewearable ultrafiltration device. Preferably the battery is rechargeableand can provide enough energy to the wearable ultrafiltration device 600for at least 6 or more hours of continuous, uninterrupted deviceoperation. The microcontroller by itself or via another circuit monitorsthe energy status of the battery 616. If the microcontroller 614determines that the battery is running low on energy or has less than anestimated predetermined amount of time left in its energy reserves, themicrocontroller 614 may trigger an alarm condition via alarm circuit 618which may provide any one or more of an audio, visual, or physical alarmsignal. The physical alarm signal may include vibrations or smalltingle-style shocks providing the patient an alarm indication that canbe felt. An alarm condition or warning condition may be displayed on thedisplay 620 using a liquid crystal, light emitting diode or otherdisplay technology. An alarm condition may also turn off an exemplarywearable ultrafiltration device 600.

A moisture sensor 622 is in communication with the microcontroller 614.The moisture sensor 622 is used to detect condensation or liquid presentinside the packaging or covering over (not specifically shown) thewearable ultrafiltration device 600. The packaging or covering may be aplastic, cloth, rubberized material or other suitable material. Thecovering may cover a portion of the ultrafiltration and allow access tothe various parts of the exemplary device.

Condensation or the presence of liquid inside the packaging or outercover of an exemplary ultrafiltration device may be indicative ofpatient blood leakage or other fluid leakage. Upon sensing moisture, themoisture sensor 622 provides a signal to the microcontroller 614 and analarm is sounded via the alarm circuit 618. Furthermore, the pump 624may be turned off by the microcontroller 614 to help minimize potentialblood loss.

The pump 624 is an electric pump. Blood from the patient is extractedvia a blood inlet tube 626. The pump 624 pumps the blood to and throughthe blood filter 628. The pump 624 is preferably powered via arechargeable battery pack 616. The microcontroller may actively adjustvarious pumping variables. Potential adjustable pump variables includeadjusting the torque of the pump motor, the pumping rate (i.e., strokesor pump cycles per minute), the pressure of the blood between the mainpump 624 and the blood filter 628.

The presently preferred pump is a single channel pulsatile pump. Ingeneral, a pulsatile pump has a rubberized cartridge with an input valveat the input end of the cartridge and an output valve at the output endof the cartridge. The motor within the pump presses the rubberized,tubular portion of the cartridge. The pressing squeezes and evacuatesthe contents of the cartridge out the open end output valve. As the pumpmotor spins and causes the mechanics of the pump to release pressurefrom the rubberized portion of the cartridge, the output valve closesand the input valve allows fluid (blood) to enter the cartridge only tobe squeezed out the output valve in the next pump cycle. The input andoutput valves are one-way valves allowing flow in a single direction. Anexemplary pump can provide a blood flow rate of about 15 to 100 ml/min(pulsatile). The approximate dimensions of the pump 624 are about9.7×7.1×4.6 cm with a weight of less than 400 grams. An exemplarypulsatile pump uses, preferably, less than 10 watts of energy. Theexemplary pump can provide low battery power and occlusion alarm signalsto the microcontroller 614.

To potentially decrease the overall energy requirement of pump 624, adual channel pulsatile style pump can be incorporated into an exemplarywearable ultrafiltration device as depicted by the dotted lines in FIG.6. The blood circuit tubing 630 split into two parallel blood routes 632before the blood pump 624 and the blood is pumped through the exemplarypulsatile style pump in parallel. After exiting the pulsatile pump thetwo parallel blood routes are recombined into a single blood route 630.By using a dual channel pulsatile pump, the pump can operate at abouthalf the rate as a single channel pulsatile pump and move the sameamount of blood. A dual channel pulsatile pump could also move bloodthrough the exemplary wearable ultrafiltration device 600 at anestimated maximum rate of about 200 ml/min or more depending on the sizeof the chambers of the maximum speed of the pump. The maximum rate canbe utilized to decrease the fluid content of the patient's blood quicklyin circumstances when the exemplary wearable ultrafiltration device isfirst turned on after being turned off for an extended period of time.

Ideally, the dual chamber pulsatile pump configuration would pump eachof the two chambers at about 180° out of phase to smooth out the bloodflow rate.

Other types of blood pumps 624 can be successfully incorporated intoembodiments of the wearable ultrafiltration device. Such other types ofpumps include, but are not limited to, a shuttle pump, a piston pump, aroller pump, a centrifuge pump, a piezoelectric pump, or otherconventional pumps. Whatever pump is utilized, the pump 624 ideally hasa manually or electrically adjusted flow rate from about 20 ml/min toabout 120 ml/min. As discussed, the main pump 624 may be controllablemanually by the user, physician or by microcontroller 614 control.

The microcontroller 614 may display pump status or other statusinformation on the display 620. User interface controls 634, buttons,switches, slide controls, knobs, connectors, infrared received etc. (notspecifically shown) may be used to enable a patient, physician, nurse orother computer device to adjust various settings and controls on anexemplary ultrafiltration device 600. For example, the pump 624 pumpingrate, torque, valve opening size, flow rate, rpm, and on/off, may all bemonitored or controlled via the user interface 632 or other deviceexternal to the exemplary ultrafiltration device 600.

After the blood passes through the main pump 624, it continues on theblood circuit 630. A reservoir 634 for containing a blood thinner oranticoagulant is part of an ultrafiltration device. A micropump 636provides the fluid contents of the reservoir 634 in a measuredcontinuous or non-continuous manner to the blood circuit 630 prior tothe blood filter 628. A micropump 636 is a type of pump that can pumpmicroscopic or miniscule amounts of fluid each minute. A micropump 636may pump a fluid in the range of 0.1 to 400 ml/hr (milliliters per hour)and requires from about 1 to 500 milliwatts to operate. There, atpresent, are various types of micropumps including, but not limited to apiezoelectric pump, a solenoid pump, micro-piston pump, peristalticpump, nanotechnology pump, microtechnology/micromachined pump, syringepump, roller pump, centrifuge pump, or diaphragm pump.

The blood thinner and/or anticoagulant may be mixed with the blood atpoint in the blood circuit between the blood inlet tube 626 and theblood filter 628.

Also in the reservoir 634, a level sensor 638 senses the amount of fluidtherein. The level sensor 638 is in electrical communication with themicrocontroller 614. The microcontroller sends an alarm signal to thealarm 618 if the fluid level in the reservoir 634 is below a firstpredetermined level or volume. The microcontroller 614 may also turn theultrafiltration device 600 off if the fluid level in the reservoir 634is below a second predetermined level or volume. The secondpredetermined level being equal to or less than the first predeterminedlevel.

The combination of reservoir 634 and micropump 636 infuse the bloodthinner or anticoagulant into the blood flowing in the blood circuit630. Presently preferred blood thinners or anticoagulants include, butare not limited to, heparin, prostacylin, low molecular weight heparin,hirudin and sodium citrate. The anticoagulant is infused into the bloodprior to the blood filter 628 and in some embodiments prior to the mainpump 624 in order to help minimize the potential of blood clots in theblood filter 628 and perhaps the main pump 624.

The blood filter 628, like the previously discussed blood filter 30, maybe a specially sized blood filter that uses conventional technology. Asillustrated, blood filter 628 includes a blood inlet 631, a blood outlet633 and a fluid outlet 635. Fluid outlet 635 is connected directly tofluid inlet 641 of fluid bladder 640A by means of tube or fluid conduit645. The exemplary blood filter 628 comprises a plurality of hollowfibers 310 that are semipourous enough to allow fluids in the form ofwater and impurities to be removed from the patient's blood withoutallowing blood cells to be removed from the blood. The hollow fibers actas a sieve such that some excess fluid passes through the semipourouswalls of the fibers without allowing blood cells to pass.

Still referring to FIG. 6, the fluids 135 filtered from the blood in theblood filter 628 are captured in a fluid bladder 640A or fluid bag. Thefluid bladder 640A may hang below the belt 602 (not specifically shown)and be able to store from about 0.1 to about 2 liters of fluid. A sensor642 is connected to the microcontroller 614 to enable an alarm 618 tosound when the fluid bladder 640A is filled to a predetermined level.Furthermore, the microcontroller 614 may turn an exemplary wearableultrafiltration device off when the level sensor 642 indicates that thefluid bladder 640A is full or has a predetermined amount of fluidtherein.

The fluid bladder 640A may contain an absorbent material (notspecifically shown) for absorbing fluid that is deposited in the fluidbladder 640A. The absorbent material may be a cotton, polymerer, driedsponge, compressed material, powder, jell, or other absorbent material.The absorbent material may perform one or more functions including, butnot limited to, limiting the movement or “sloshing” of the fluid in thebladder, to expanding the bladder so the patient will know that thebladder is full, to expand the fluid bladder so that it exerts pressureor weight against a microswitch (not specifically shown). Themicroswitch may be used to provide a signal to the microcontroller thatindicates the fluid bladder is full, to create a conductive or ionicsource to enable a moisture sensor or fullness sensor to operate andprovide a fluid bladder fullness signal to the microcontroller.

Fluid bladder 640A may have a means for emptying the fluid bladderthereon in the form of a manual or electro mechanical valve. In anembodiment a valve 644 may be opened to drain the fluid from the fluidbladder 640A. In another embodiment, the fluid bladder 644 is detachableand disposable.

In another embodiment of the wearable ultrafiltration device 600, asmall reservoir 640B is either part of or connected to the blood filter628. A small pump or micropump 647 transfers the filtered fluids fromthe small reservoir 640B into a belt mounted container or reservoir 648.The small pump or micropump 647 may also provide vacuum pressure ornegative pressure to the blood filter 628 thereby potentially increasingthe filtering effect and the rate of fluid removal from the blood. Thesmall or micropump 647 may also be used to eliminate the fluid bladder640B by pumping fluids directly to fluid container 648. The fluidcontainer 648 may comprise a fullness or fluid level sensor 649. Thefullness sensor 649 may be a microswitch or pressure sensitive sensorthat senses a fullness of a bladder (not specifically shown) inside thebelt reservoir 648. As the bladder, within the belt reservoir 648 fills,the bladder presses against the fullness sensor 649 and a fullnesssignal is received by the microprocessor. A material or device thatexpands when it absorbs or is in the presence of fluid may be containedwithin the belt reservoir 648. The material or device within the beltreservoir 648 may be a bladder, cotton, pressed sponge-like material, anabsorbent powder or pellet substance that expands, absorbs or becomesthick or jell-like when wet. Absorbent material within the beltreservoir 648 may also minimize or eliminate a sloshing of any fluidcontained therein. The belt mounted fluid reservoir 648 eliminates aneed for a hanging bag or bladder to collect waste fluids. The beltmounted fluid reservoir may be easily attached and detached from anexemplary ultrafiltration device 600 for emptying by the patient.

As the blood flows through the blood circuit 630, excess fluid and bloodcontaminants are separated from the blood via ultrafiltration at theblood filter. The excess fluid 135 is removed from the blood filter 628as it sweats or percolates through the walls of the hollow fibers 310.It is understood that various types of blood filters or dialyzer devicesmay be used in an exemplary embodiment.

Since embodiment of the present ultrafiltration device is intended to beworn by a patient on or as part of a waist self or shoulderharness/strap, it is somewhat important for an exemplary ultrafiltrationdevice to function regardless the ultrafiltration device's relativeorientation with respect to being horizontal with the ground. In otherwords, an exemplary ultrafiltration device should be operationalregardless of whether the patient wearing the device is standing,sitting, lying down, or upside down. Thus, embodiments of the presentultrafiltration device operates in any three-dimensional orientation sothat the device will operate twenty-four hours a day regardless whetherthe patient is standing, sitting or lying down.

Other embodiments of the present invention may have a sensor thatdetermines whether ultrafiltration device is an operational orientation.If the ultrafiltration device is not in an orientation wherein it willoperate properly, then the sensor will turn off or shut down the pumpsvia a switch or microprocessor control.

An exemplary ultrafiltration device is light enough to be completelywearable by a patient. An exemplary ultrafiltration device weighsbetween one and five pounds (with or without fluids).

Various experiments were performed with an exemplary ultrafiltrationdevice. The exemplary ultrafiltration device was being used to treatfluid overload. Animals, in particular, six pigs, were used to test anexemplary ultrafiltration device. Each pig underwent bilateral urethralligation to produce acute renal failure and fluid overload. After 24 to48 hours each animal was anesthetized and a double lumen catheter wasinserted in their jugular vein. The cartoid artery was canulated forblood sampling.

The double lumen catheter was connected to the exemplary device and theblood was ultrafiltered. The device consisted of a hollow fiber dialyzerand a port for heparin infusion. Heparin was administered into the bloodcircuit regularly to prevent the clotting of blood in the device. Abattery-operated pulsatile pump (FIG. 1) propelled the blood through thedevice. The total weight of the pump and the hollow fiber dialyzer wasless than 2.5 lbs. The design of the device used in the test is shown inFIG. 1.

The general results of the experiments are as follows:

-   -   The blood flow rates through the device ranged between 0 and 200        ml per min.    -   The average blood flow was about 44 ml/min.    -   The amounts of fluid removed from each animal (ultra filtration)        by the device ranged from 0 to 700 ml/hour and is tabulated in        Table I.

The amount of fluid removal was manually adjusted by partially orcompletely occluding the exit of the ultrafiltrate to the collectionbag. Again, the hourly amount of fluid removed ranged from 0- to700-ml/hr.

There were no complications or untoward effects on the animalsattributable to the ultrafiltration during the experiments.

TABLE I Amount of fluid removed (in ml.) from each animal in eighthours. Pig C Pig D Pig E Pig F Pig G Pig H (g) (g) (g) (g) (g) (g) 1 hr400 100 100 100 150 180 2 hrs 700 200 200 200 220 200 3 hrs 300 200 300380 350 4 hrs 800 400 250 400 500 700 5 hrs 500 300 500 600 710 6 hrs500 500 800 680 1410 7 hrs 620 600 1000 700 1400 8 hrs 800 1000 1150 8001400 Average 100 100 125 144 100 175 The last row depicts the averagehourly rate of ultrafiltration.

The results of the experiment merits additional discussion because ofthe successful controlled removal of fluid from the pigs blood. There isa growing notion and body of literature supporting the hypothesis thatblood ultrafiltration is an effective tool in the treatment of class IIIand IV CHF patients. There seems to be significant effects on theelectrolyte and endocrine derangements associated with this condition aswell as an avoidance of diuretics that are so often conducive to renalfailure, hypotension and further metabolic complications. However, thispresently can only be accomplished by using a dialysis machine or otherultrafiltration device that is not amenable to be used substantiallycontinuously while a patient is ambulatory. The aim of the presentexperiments was to evaluate the efficiency and actual fluid removal withan exemplary miniaturized ultrafiltration device.

The exemplary ultrafiltration device operated very well in terms ofremoval of plasma ultrafiltration at a wide range of flow rates andvolumes. Fluids were removed from the blood at rates ranging from 0 to700 ml/hr without difficulty, except for a decrease in blood flowthrough the exemplary ultrafiltration device as fluid removal wasincreased beyond about 700 ml/hr. It is believed the difficulty isattributable to the marked hemoconcentration inside the hollow fibers ofthe blood filter as a consequence of removing too much water. Decreasingthe rate of ultrafiltration resulted in a return of the blood flow tothe previous rate. Another possible technique for maintaining ampleblood flow with a high ultrafiltration rate is to utilize a blood filterhaving hollow fibers or lumens with a larger inner diameter, for exampleup to 1 mm in diameter or utilizing a different shaped lumen forexample, one having an oval or oblong cross-section having a largercross-sectional area.

The exemplary ultrafiltration device proved effective at removing largequantities of water from a patient at virtually any rate a treatingphysician might desire. As a result an exemplary wearableultrafiltration device may be valuable for the treatment of fluidoverload, specifically in CHF patients.

Using a blood flow in the range of 10 to 70 ml/min, and preferablyaround 44 ml/min, make it unlikely that patients may experience bluntcompartment shifts or hemodynamic compromise in otherwise very illpatients.

An exemplary wearable ultrafiltration device can, unlike other alreadyexisting ultrafiltration devices, be completely worn and be operationalfor treating a patient by ultrafiltration 24 hours a day, seven days aweek in a substantially continuous manner. The treatment can be appliedin a hospital or in an ambulatory condition.

An exemplary wearable ultrafiltrate device can be used to effectivelyreduce a patient's incidence of acute pulmonary edema, ascites, andother stigmata of class III and IV CHF.

An additional aspect of an embodiment of the present wearableultrafiltration device is that a patient who utilizes the device may beable to significantly reduce their usage of diuretics and other CHFrelated drugs. Embodiments of the present invention are also effectiveat removing sodium along with fluids. Since sodium retention is one ofthe problems related with CHF, CHF patients are usually condemned todraconian restrictions of salt intake, commonly 2 to 3 grams per day. Onthe other hand, the sodium concentration in the ultrafiltrate producedby an embodiment of the present device is equal to the concentration inthe blood plasmas (i.e., about 0.9 grams of salt per 100 ml). Thus,steady removal about 1.5 to 2 liters of ultrafiltrate from a patienteach day results in the removal of about 13.5 to 18 grams of salt orsodium per day from the patient. This result would not only eliminate orreduce a patient's salt restriction and the need for diuretics and otherdrugs, but also may result in having to encourage the patient to eatfoods with more salt. The impact of an exemplary device on a patient'squality of life by reducing CHF related shortness of breath, legswelling and ability to enjoy salt in their food will be significantlypositive, but difficult to quantify.

It is expected that outcomes in the treatment of CHF patients, namely asignificant reduction in morbidity and mortality will be significant,but further clinical studies are needed to quantify these potentialresults. Embodiments of the present invention may provide economicimpacts by reducing the length of patient hospital stays, ICU needs anddrug consumption. The overall economic impact and value remains to bestudied.

Thus, it is seen that a wearable ultrafiltration device is provided. Oneskilled in the art will appreciate that the present invention can bepracticed by other than the preferred embodiments which are presented inthis description for purposes of illustration and not of limitation, andthe present invention is limited only by the claims that follow. It isnoted that equivalents for the particular embodiments discussed in thisdescription may practice the invention as well.

The previous description is of a preferred embodiment for implementingthe invention, and the scope of the invention should not necessarily belimited by this description. The scope of the present invention isinstead defined by the following claims.

1. A portable, wearable ultrafiltration device comprising: a blood inletfor receiving blood flow from a patient; a pump for pumping said blood,from said patient, through said ultrafiltration device at a blood flowrate, said pump adapted to receive power from a battery; a blood filterfor filtering fluid from said blood, the rate of fluid filtering fromthe blood is configured to be adjusted by a combination of the bloodflow rate and by controlling a continuous fluid flow from the bloodfilter; a blood outlet connected to the blood filter, the blood outletconfigured to receive blood from the blood filter and return the bloodto the patient; a fluid bladder, in removable fluid communication withsaid blood filter, for collecting said fluid, the wearableultrafiltration device constructed and configured to operate while invarious three-dimensional orientations on the body of the patient; analarm for providing an alarm indication to said patient; amicrocontroller electrically connected to the battery, the pump and thealarm, the microcontroller sensing a battery charge and providing analarm signal to said alarm if said battery charge is below apredetermined level.
 2. The portable, wearable ultrafiltration device ofclaim 1, wherein said pump weighs less than 400 grams.
 3. The portable,wearable ultrafiltration device of claim 1, wherein said pump is apulsatile pump adapted to pump blood at a flow rate between 40 and 200ml/hr.
 4. The portable, wearable ultrafiltration device of claim 3,wherein said pump requires less than 10 watts of energy.
 5. Theportable, wearable ultrafiltration device of claim 1, said pump is adual chamber pulsatile pump.
 6. The portable, wearable ultrafiltrationdevice of claim 1, wherein said battery is rechargeable.
 7. Theportable, wearable ultrafiltration device of claim 1, wherein saidbattery is adapted to be removable.
 8. The portable, wearableultrafiltration device of claim 1, wherein said alarm indication is atleast one of an audible, visual, a felt sensation indication.
 9. Theportable, wearable ultrafiltration device of claim 1, further comprisinga bladder sensor for sensing a fullness of said fluid bladder andenabling a full fluid bladder signal to be received by saidmicrocontroller.
 10. The portable, wearable ultrafiltration device ofclaim 9, wherein said micro controller sends an off signal to said pumpafter receiving said full fluid bladder signal.
 11. The portable,wearable ultrafiltration device of claim 1, wherein said fluid bladdercontains an absorbent material.
 12. The portable, wearableultrafiltration device of claim 11, wherein said absorbent materialexpands as it absorbs fluid.